Growth rate and surface morphology of 4H–SiC crystals grown from Si–Cr–C and Si–Cr–Al–C solutions under various temperature gradient conditions

The growth rate and surface morphology of 4H–SiC crystals prepared by solution growth with Si1−xCrx and Si1−x−yCrxAly (x=0.4, 0.5 and 0.6; y=0.04) solvents were investigated under various temperature conditions. The growth rate was examined as functions of the temperature difference between the growth surface and C source, the amount of supersaturated C and supersaturation at the growth surface. We found that generation of trench-like surface defects in 4H–SiC crystals was suppressed using Si1−x−yCrxAly solvents even under highly supersaturated conditions where the growth rate exceeded 760 µm/h. Conversely, trench-like defects were observed in crystals grown with Si1−xCrx solvents under all experimental conditions. Statistical observation of the macrostep structure showed that the macrostep height in crystals grown with Si1−x−yCrxAly solvents was maintained at lower levels than that obtained using Si1−xCrx solvents. Addition of Al prevents the macrosteps from developing into large steps, which are responsible for the generation of trench-like surface defects.